Along with the commercialization progress of electric vehicles, a vehicle-mounted charger of the electric vehicles has become one of important components in the electric vehicles.
There are many methods for charging the whole vehicle and for outwardly discharging from the whole vehicle via the vehicle-mounted charger. A monophase H bridge control method is mostly adopted in related arts, which includes a dual-polarity control method and a mono-polarity control method.
However, when the dual-polarity control method is adopted, four switch transistors in an H bridge are all in a high frequency ON/OFF state, resulting in higher switching loss and larger heat loss. When the mono-polarity control method is adopted, although the heat loss of the switch transistors that is generated when the dual-polarity control method is adopted can be solved to some extent, the four switch transistors in the H bridge are controlled according to a fixed manner during a charging process or a discharging process of the whole vehicle, some switch transistors in the H bridge need to be switched off with current. The overheat problems of the switch transistors switched off with current are not effectively solved.
Therefore, regardless of whether the dual-polarity control method or the mono-polarity control method is adopted, the heating problems of the switch transistors in the H bridge cannot be effectively solved, and the service life of the switch transistors is affected.